Apparatus for stopper removal

ABSTRACT

Stoppers are separated from tubes they close by suspending a stoppered tube by its stopper, placing the suspended tube in a swinging bucket centrifuge, subjecting the suspended tube to centrifugal force. 
     This may be accomplished by adapting a test tube rack to be placed in a centrifuge&#39;s swinging bucket type carrier. The rack is a two piece unit having upper and lower members that are separable. The test tubes use stoppers having an enlarged portion with a diameter which exceeds that of the test tube such that the tubes may be suspended from the upper member by their stoppers. The rack has a height which exceeds that of the test tubes such that when the rack with the tubes suspended therein are subjected to centrifugal force, the tubes withdraw from the stoppers. This leaves the stoppers positioned on the upper surface of the upper member. If now the upper member is lifted away, the stoppers are removed leaving the unstoppered test tubes positioned in the lower member of the rack.

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for automaticallyremoving stoppers from test tubes.

In many fields, it is necessary to use test tubes having caps orstoppers. Such usage implies that at some point in time, it may bedesirable to remove the stopper. When large numbers of test tubes areused, such stopper removal can require an excessive amount of time. Inaddition, in the medical and blood testing fields, when dangerousmaterials are being handled, the removal of such stoppers poses nolittle danger to the operator or lab technician who in most instancesmust remove such stoppers manually. Manual stopper removal can result indropping or spraying minute droplets of the tube contents onto the labtechnician. This presents a particular problem particularly if thecontents of the tubes are infectious or pathogenic.

Some little improvement over individually removing the stoppers fromeach tube is offered in the teachings of U.S. Pat. 3,649,464 issued Mar.14, 1972, to Freeman. This patent teaches the use of multiple stoppersbeing attached to a lifting tab. While this speeds up operations, thedanger to the technician remains.

It is, therefore, an object of this invention to provide a relativelysimple method and apparatus that is capable of quickly and safelyremoving the stoppers from test tubes while reducing any danger to theoperating personnel.

SUMMARY OF THE INVENTION

According to a preferred apparatus of this invention, stoppers areremoved from fluid filled test tubes while the tubes' contents are beingcentrifuged, by pivotally suspending the test tubes by their respectivestoppers, rotating the suspended tubes about an axis transverse to theseveral tube axes to cause the respective tubes to separate from theirrespective stoppers under the influence of centrifugal force, andfinally supporting the separated tubes.

A preferred apparatus for performing this method uses a centrifugehaving a swinging type bucket carrier. Such apparatus includes a rackadapted to be placed in the bucket type carrier and having upper andlower separable members, the upper member having an upper surfacedefining plural apertures adapted to receive the test tubes, eachstopper having an enlarged portion with an outside diameter greater thanthe diameters of its associated test tube and said apertures, thereby topermit said test tubes to hang from the rack's upper surface supportedonly by their respective stoppers, the lower member having a bottom,supporting means associated with the lower member for supporting thetest tubes against lateral movement, the distance from the bottom of thetest tubes to the enlarged stopper portion being less than the distancefrom the upper surface to the lower member's bottom, whereby subjectingsaid rack to centrifugal force withdraws the tubes from the stoppers torest on said lower member's bottom such that the stoppers can bediscarded and access had to the contents of the test tubes.

This apparatus, which is capable of use in a centrifuge for theautomatic removal of stoppers, has a particular advantage in that theoperators are not exposed to the hazards of the contents of the testtubes. A second advantage accrues from the fact that the stoppers areremoved substantially simultaneously from all of the tubes positioned inthe rack while the contents of the tubes are being centrifuged. Thisappreciably reduces the time required for normal stopper removal and, inany event, does not require an extra step. As soon as the centrifuge isstopped, the tube contents are exposed and ready for further processing.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of this invention will become apparentupon consideration of the following description in which:

FIG. 1 is an elevation view, partially cut away, of a test tube rackcapable of performing the method of this invention constructed inaccordance with a preferred embodiment particularly depicting test tubessuspended in the rack by their stoppers;

FIG. 2 is an exploded view, partially cut away, of the test tube rackillustrated in FIG. 1;

FIG. 3 is a plan view, partially cut away, of a test tube rack forsupporting suspending test tubes by their stoppers, constructed inaccordance with a second embodiment of this invention;

FIG. 4 is a section view of the test tube rack of FIG. 3 taken along thesection line 4--4;

FIG. 5 is a cross-sectional elevation view of the test tube rack of FIG.3, taken along the section line 4--4, but in this instance depicting thetest tube after its separation from the stopper by centrifugal force;

FIG. 6 is a schematic illustration of a swinging bucket centrifuge withits bucket carrier in an operating position and holding racks withstopper suspended test tubes; and

FIG. 7 is another alternative adapter rack that may be used in themethod of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There may be seen with reference to FIGS. 1 and 2 a first and preferredembodiment of an apparatus for automatically removing stoppers from testtubes in accordance with the method of this invention. The apparatusdepicted in FIG. 1 is seen to include a rack 10 that is adapted to beplaced in a centrifuge such as that illustrated diagrammatically in FIG.6. The apparatus of FIG. 6 constitutes a centrifuge rotor 12 of aconventional type which may pivotally mount at 16 a swinging bucket typecarrier(s) 14. The carrier 14 may be a conventional omni type carriersuch as that designated by the Model #00598 available from E. I. du Pontde Nemours and Co., Wilmington, DE, which is adapted to be pivotallyhung on a horizontal rotor 12 for supporting various adapters.Alternatively, the carrier may be a bucket, of conventional design,structed to receive tube adapters. The horizontal rotor may be a typicalfour-piece unit such as Model #HL4 also available from E. I. du Pont deNemours and Co. The rotor 12 is removably positioned on a gyroscopemount 18 of a conventional centrifuge adapted to be driven by a motor,depicted by the block 20 operating through a suitable linkage depictedby the dashed line 22.

The swinging bucket carrier 14 illustrated has a bottom platform 24adapted to hold a pair of racks 10 constructed in accordance with apreferred embodiment of this invention. The centrifuge depicted in FIG.6 is illustrated in its operating position with the carrier 14 pivotedoutwardly from its normally vertical hanging position when at rest suchthat centrifugal force is exerted axially of tubes suspended in theracks 10 as will be described.

The racks 10 are seen to comprise an upper member 26 and a lower member28. Both of the members of this embodiment are shell-like with the edgeportions 27 of each member in mating relationship such that the upperand lower members 26 and 28, respectively, (each illustrated here asgenerally rectangular in shape) form a box-like enclosure. The matingedges 27 define a step-like interfit or joint 30 (FIG. 1) such that theupper member 26 fits into the lower member 28 and yet may be easilyremoved by lifting the upper member 26 away from the lower member 28.The upper member 26 has an upper surface 32 in which are formed aplurality of apertures or holes 34 sized to accommodate with a loosesliding fit a corresponding plurality of test tubes 36 of conventionaldesign.

Each of the test tubes may be of any suitable material typically used inchemical, medical or centrifuge applications. Each tube has a cap orstopper 38 typically constructed of a resilient material such as rubber.Such stoppers are constructed such that at least the upper portionthereof is enlarged to have a diamter (or at least portions of thediameter) which exceeds the outer diameter of the test tubes 36. Typicalof these tubes are evacuated blood collection tubes such as those soldfor blood work by Becton Dickinson and Company, Rutherford, N.J. underthe tradename "Vacutainer". In this manner, the test tubes 36 may besuspended along their axes 37 from the enlarged stoppers 38 and hence,supported solely by the upper member 26 of the rack 10.

The lower member 28 also is box-like and is provided with a bottomsurface 40 for supporting the unstoppered tubes as will be described. Aresilient pad 44, made of rubber or the like, is placed over the bottom40 of the lower member 28 to permit the test tubes 36 to drop to asupporting surface without breaking, i.e., the pad is able to cushiontheir fall when they are subjected to centrifugal force and henceprevent such damage or breakage of the tubes. A lattice-like, lateralsupport 46 is adapted to fit in the lower member 28 defining a pluralityof (rectangular) openings 48 that are in alignment with each of theopenings 34 in the upper surface 32 such that each of the supportopenings 48 may receive an individual tube 36. In this manner, once theupper member 26 is removed, after the tubes are resting on the rubberpads 44, the tubes are provided with a lateral support to prevent theirfalling. The lattice may be shaped if desired to more closely conform tothe tubes'-round configuration. The lattice and the racks may be formedof a suitable rigid metal or plastic.

To facilitate stopper removal from the tubes, the combined distancebetween the bottom support plate 40 and the upper surface 32 of theupper member, when in stacked or mating array, exceeds the distancemeasured from the bottom of the tubes up to the bottom of the enlargedportion 38 (or the bottom of any insert 39 on the stoppers). The tubesare suspended with a spacing typically of some 12 to 13 millimeters (forevacuated blood tubes) above the bottom 40 (or pad 44) of the lowermember 28. This spacing must be sufficiently great such that as thetubes are urged downwardly in the drawing by the centrifugal force,there is sufficient clearance that they may be pulled or withdrawnentirely from the stoppers 38 suspended from the top surface 32.Preferably, the clearance should be one to two millimeters greater thanthe axial length 37 of those portions of the stopper 38 which contactsby the tube, i.e., the tubes must be permitted to drop sufficiently tobe free of any portion 39 of the stoppers which grip the tubes with asufficient force to hold the tubes in a suspended state.

The stoppers may be caps having downwardly extending skirts 41 whichcontact only the exterior of the upper lip portion of the test tubes orthey may also have an insert 39 which fits inside of the upper lipportion. In some cases, the skirt portion 41 is omitted. In operation,the tubes 36 with their stoppers 38 engaged, i.e., the tubes arestoppered, are each positioned in a different hole 34 in the top surface32 of the rack with the tubes suspended by their stoppers from the topsurface 32. In this instance, the rack is in assembled form with the topmember 26 engaged with the bottom member 28 to form the hollow box-likeassembly illustrated. The rack 10 or several racks, as the case may be,are loaded with filled tubes to be centrifuged and destoppered andplaced within the centrifuge carriers of FIG. 6 and the centrifugeoperated with sufficient speed to cause the carriers to swing out (FIG.6). In this manner, the axes 37 of the tubes are transverse to the spinaxis (18) of the centrifuge. The contents of the tubes are centrifugedat the same time the stoppers are being removed. As the rotation speedincreases, the tubes are urged away from their stoppers 38 bycentrifugal force and into contact with the rubber pad 44 on the bottomof the lower member 28. The centrifuge is stopped, allowing the carriersto fall back to the vertical and the rack(s) 10 placed on a convenienttable, at which time the operator simply lifts off the top member 26carrying the stoppers 38 therewith. These stoppers may then be discardedwith little or no danger to the operator. Note the removal of the tubesfrom the stoppers typically occurs substantially simultaneously duringthe centrifugal action. There is little danger to the operator ortechnician since the stoppers themselves need not be handled orotherwise touched with human hands following their removal. Furthermore,human hands were not a part of the actual removal in the operationthereby even further reducing any potential danger to the operator.Since the stopper removal takes place simultaneously with thecentrifuging of the tube's contents and for all of the tubes in therack, significant savings in time are achieved. It is to be noted thatthe centrifugal force needed simply to remove stoppers is not greatsince a relatively small amount of force is required to remove the tubesfrom the stoppers.

In an alternative embodiment of the invention, a simple rack of the typedepicted in FIGS. 3 and 4 is constructed. This rack 60 may beconstructed of two pieces; an upper piece 62 and a lower piece 64. Bothof the pieces 62 and 64 may be constructed of sheet metal such asstainless steel of sufficient gauge so as to withstand the rigors ofcentrifugal action. Alternatively, they may be molded of a suitableplastic. The dimensions of the racks 60 are somewhat similar to thedimensions described in conjunction with the embodiment of FIG. 1. Inthis instance, the upper member 62 is constructed to be U-shaped withthe open end of the U having clips or pins 66 adapted to engagereceptacles 68 formed in the open end of the bottom piece 64 which alsognerally U-shaped. The upper surface 70 of the upper member 62 is formedwith a plurality of apertures or holes 72 formed therein, adapted toreceive the test tubes 36 having stoppers 38 of the type describedherein above. The bottom member 64 also is adapted to have a resilientpad 44 placed on the bottom thereof as described previously. Inaddition, the upwardly extending arms of the U-shaped bottom piece 64are joined preferably by two intermediate plates 74 each of which hasapertures or holes 76 formed therein in alignment with the correspondingholes 72 in the upper plate 70 such that the tubes 36 may slide throughthe upper holes 72 and be received in the holes of the intermediateplates 74. As seen in FIG. 4, the tubes 36 are suspended from the topplate 70 by the stoppers 38. The rack may then be placed on the carriers14 (FIG. 6) of a centrifuge.

During centrifugal action, the tubes 36 drop or are withdrawn from thestoppers such that their bottoms rest on the resilient pads 44 (FIG. 5)and are supported from lateral movement by the intermediate plates 74.Thus, as soon as the centrifugal action stops and the racks removed fromthe centrifuge, the upper rack 10 may be simply lifted off, the stoppers38 discarded, leaving the open-ended tubes 36 ready for test, analysisand the like. Following such tests or analysis, the tubes are removedand the racks stand ready for use and re-use.

Still another apparatus for effecting the method of this invention isillustrated in FIG. 7. This apparatus includes a conventional tubeadapter 80 adapted to be housed in a swinging bucket centrifuge rotor.The adapter has axial bores 82 adapted to receive tubes. A disc-likesection 84 having bores 86 aligned with the bores 82. The combinedheight of the bores 86 and 82 must exceed the tube bottom to stopperdistance as previously described. Both the adapter 80 and the section 84fit in the bucket preferably with the upper portions of the section 84extending slightly out of the bucket (not shown). A lifting handle forthe section 84 may be provided if needed. Once the stoppers are removed,section 84 need only be lifted and the stoppers discarded leaving thecentrifuged tubes opened and ready for further processing.

There has thus been described a relatively simple method and apparatusfor the centrifugal removal of the stoppers of test tubes. The methodand apparatus provided have many advantages in that they permit thesimultaneous removal of all stoppers from a group of tubes while theyare being centrifuged and has the unique advantage of reducing anydanger inherent in such removal to the operator.

What is claimed is:
 1. Apparatus for removing stoppers from test tubesusing a centrifuge having a swinging bucket-type carrier comprising, incombination,a rack to be placed in said bucket-type carrier and havingupper and lower separable members, said upper member having an uppersurface defining plural apertures receiving said test tubes, at least aportion of each said stopper having an enlarged portion with an outsidediameter greater than the diameter of its associated test tube, therebyto permit said test tubes to hang from said upper surface supported onlyby their respective stoppers, said lower member having a bottom,supporting means associated with said lower member for supporting saidtest tubes against lateral movement, and the spacing between the bottomof said test tubes and said lower member bottom being greater than thelength of the stoppers along the axis of said tubes in contact with saidtubes, whereby subjecting said rack to centrifugal force separates saidtest tubes from said stoppers to rest on said lower member bottom suchthat said stoppers can be discarded and access had to the contents ofsaid test tubes by removing said upper member from said lower member. 2.Apparatus according to claim 1 wherein said lower member bottom iscovered by a resilient pad.
 3. Apparatus according to claim 2 whereinsaid supporting means is a horizontal plate secured to said lower memberand defining openings adapted to receive said tubes.
 4. Apparatusaccording to claim 2 wherein said supporting means is a lattice-likeinsert receiving the lower portion of said test tubes.
 5. Apparatusaccording to claim 1 wherein said supporting means is a horizontal platesecured to said lower member and defining openings receiving said tubes..[.6. A method of simultaneously centrifuging the contents of andremoving a stopper from a fluid filled stoppered test tube having anaxis intersecting said stopper, comprising the steps of:suspending saidtest tube by said stopper, subjecting said suspended tube to centrifugalforce along said tube axis to cause said tube and contents to separatefrom said stoppers under the influence of said centrifugal force, andsupporting said separated tube..].